Limit yourself to 90 minute shifts during your normal sleeping hours. Make sure your headlights are aimed properly and the lenses are clean, to give you as much light as you can (though hi-beams are normally not necessary on a well-traveled interstate.) If you normally wear contacts to drive, carry wetting drops and/or be prepared to take them out and use driving glasses instead. Eyestrain is the most common reason for night-driving accidents, as it takes a lot of energy to keep your eyes focused on a highway in the dark.
Try not to eat too heavily at dinner, but do eat protein.
I also love audio books for driving, the funnier or more suspenseful the better. I prefer to use my bluetooth earpiece rather than full headphones when driving, as I think they block out a bit too much of the other noise around you. If you have a decent public library system, you should be able to download a variety of titles at no charge. (BTW, for keeping the kids entertained when they are awake, I find that the Kingdom Keepers book series is great fun on WDW road trips, as the books are set there. They are meant as young adult novels, so they won't bore the adults to tears, but they are OK for a school-aged audience.)